no, this is not a frequent illness
this sounds like it could be a type of mental illness he has.
this symptom is called paranoia and can be in patients who have severe depression or schizophrenia or severe anxiety disorder.
your friend needs to see a doctor or psychiatrist or one of the health workers at the school health clinic to be evaluated for these paranoia symptoms.
he may need medication or psychotherapy treatment to help his symptoms.
let me know if you have other questions.
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